Why has the boolean modifier created new vertices?
The topology you see in wireframe mode is real topology of your mesh if the modifiers were applied. The edges (and not vertices) are added because it is impossible in Blender (as far as i know) to have a face with an hole in it, with a connected vertex. To create a hole you need to create a cut to join the two edge loop of the new face.
The wireframe view can avoid to display some edges if the faces have the same normal, but for that you need to apply the modifiers, then go to Edit Mode and back to Object Mode.